1. Field of the Disclosure
The technology of the disclosure relates to creating optical surfaces at the end portions of optical fibers disposed in ferrules as part of fiber optic connector assemblies to establish fiber optic connections.
2. Technical Background
Benefits of utilizing optical fiber include extremely wide bandwidth and low noise operation. Because of these advantages, optical fiber is increasingly being used for a variety of applications, including but not limited to broadband voice, video, and data transmission in communications networks. As a result, communications networks include a number of optical interconnection points in fiber optic equipment and between fiber optic cables in which optical fibers must be interconnected via fiber optic connections. To conveniently provide these fiber optic connections, fiber optic connectors are provided. A fiber optic connector includes a housing that provides internal components for receiving, supporting, protecting, and aligning one or more end portions of optical fibers exposed from a fiber optic cable(s) when mated with other fiber optic connectors or adapters provided in fiber optic equipment or fiber optic cables. Fiber optic connectors may be installed on fiber optic cables in the field. Alternatively, fiber optic cables may be “pre-connectorized” during the manufacturing of the fiber optic cables.
To receive, support, and position an optical fiber in a fiber optic connector, a ferrule is typically provided in the fiber optic connector. A ferrule is a component that receives, supports, and positions an optical fiber(s) in a known location with respect to a housing of a fiber optic connector. Thus, when the housing of the fiber optic connector is mated with another fiber optic connector or adapter, the optical fiber(s) in the ferrule is positioned in a known, fixed location about the housing of the fiber optic connector. Thus, the optical fiber(s) are aligned with other optical fiber(s) provided in the mated fiber optic connector or adapter to establish an optical connection(s). In some fiber optic connectors, a “blind hole” ferrule is provided that includes an opening to receive an optical fiber and align the optical fiber with a lens disposed in the ferrule. In other fiber optic connectors, a “pass-through” ferrule is provided that includes a front opening and a rear opening on each end of a bore that allows an optical fiber to pass through the bore and through the front opening to extend past the front end face of the ferrule.
Whether a fiber optic connector includes a “blind hole” or “pass-through” ferrule, the end portion of the optical fiber may be polished during the connectorization process. Polishing the end portion of an optical fiber can reduce or eliminate scratches, cracks, or other blemishes that could otherwise cause optical attenuation. Polishing the end portion of the optical fiber prepares an optical surface on an end face of the optical fiber for low attenuation optical signal transfer. In fiber optic connectors employing “pass-through” ferrules, the height of the optical surface from the rear end face of the ferrule may also need to be precisely controlled as part of polishing to minimize an air gap between mated optical fibers and/or to meet fiber optic connector industry standards (e.g., consistent with International Standard CEI/IEC 61755-3-2).
Mechanical polishing processes can be employed, but are labor-intensive. For example, in a mechanical polishing process, optical fibers are manually routed through and secured within a ferrule such that an end portion of the optical fiber extends past a front end face of the ferrule at an initial height. The end portion of the optical fiber is then mechanically polished to create an optical surface at the desired height from the front end face of the ferrule. Mechanical polishing equipment can be expensive and not have the desired manufacturing throughput. For example, mechanical polishing equipment may include a fixture that is configured to support multiple ferrule assemblies for polishing as part of a batch process. At various stages of polishing, the ferrules and respective optical fibers may be removed, cleaned, and inspected. Also, this human involvement can lead to optical surface variations in mechanical polishing processes.
To minimize defects in prepared optical surfaces of optical fibers and improve manufacturing productivity, laser polishing may be employed. Laser polishing involves exposing the end portion of the optical fiber extending from the end face of a ferrule to a laser beam. This exposure can be controlled to create an optical surface in the end portion of the optical fiber. However, it may be difficult or not possible to control a laser beam envelope to create a desired optical surface in the end portion of the optical fiber at the desired height from the end face of the ferrule without also exposing the ferrule to the laser beam. Exposing the ferrule to the laser beam can damage the ferrule. Thus, if laser polishing processes are employed, so as to not expose the ferrule to the laser beam, the laser beam is controlled to create an optical surface in the end portion of the optical fiber at a larger distance from the end face of the ferrule. Then, a separate mechanical polishing process can be employed to reduce the height of the optical surface from the end face of the ferrule to create the desired height of the optical surface. Mechanical polishing of optical fibers involves human processing and associated labor costs. Mechanical polishing also introduces variances between prepared optical surfaces in ferrule assemblies.